Oscillograph



3 Sheets-Sheet 1 G. M. RASSWEILER El' AL oscILLoGRAPH Filed Jan. 14, 1931 .ji I! E w Nu x n Feb. ll, 1936.

Feb. 1l, 1936.

G. M. RASSWEILER ET AL OSC ILLOGHAPH Filed Jan. 14, 1951 l l y il! 1a., /J/

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3 Sheets-Sheet 3 gmnnou hama Feb. 11, 1936 UNITED STATES PATIEINTv .OFFICE- osclLLoGaAPn Application January 14, 1931, Serial N0. 508,666

Claims.

This-invention relates to an oscillograph. It

certain improvements over prior instruments oi' its kind. which improvements are designed to better the operation and to add to its range of usefulness especially when used with an engine indicator o! a known kind, and having characteristics resembling those of the electric 'telemetric device shown in the patent to Peters,

1,528,627, March 3, 1925.

Among the objects sought to be attained by the present invention are an improved adjustable zmounting for the source of light with relation to the instrument proper. Y

An'improved drive for the rotating mirror used i with instruments oi' this kind.

` improved shutter combined with a slit for the passage of the light beam, and mechanism therewith to adiustably determine the lcilective dimension of the silt, together with magy netically operated mechanism to open the shut- A "combined viewing screen and film holder 'whereby the light diagram may be observed or photographed by merely sliding the combined unit. e'

-An arrangement for denitely locating on the light diagram points corresponding to top and bottom dead centers of the engine piston, or other predetermined points as desired.

) An arrangement for locating on the light diagram a, point corresponding with the instant oi ignition. y

The instrument affords the opportunity of combining several related and associated accessory instruments on a single panel, preferably one of the lside panels of the oscillograph, this panel being then a base for mounting such instruments as the engine indicator bridge, meters, resistance coils, and switches.

J The above and other associated objects are accomplished by the structure constituting the improved device shown in the accompanying drawings and described below.

In the drawings- 5 Fig. l is a. diagrammatic view.

. Fig. 2 is a vertical longitudinal section.

Fig. 3 is a horizontal section, parts being shown in elevation.

Fig. 4 is a vertical section on line l--l of Fig. 2. Fig. 5 is a side elevation of the shutter assembly.

l Fig. 6 is a perspective oi the shutter assembly.

Fig. 7 is a side elevation of a detail, the cylin- 5 drical lens.

(Cl. P11- 95) Fig. 8 is a side elevation oi a part of the vertical light shield.

Fig. 9 is a ditic view showing the association of a transformer with the galvanometer coil.

Referring by reference characters to Fig. l of the drawings, A is a box-like housing. Light from a. source B passes through a lens C, a shutter D, and isreilected from an oscillating reector E constituting a part of the galvanometer. The beam then passes through a cylindrical lens F and is reilected from a face of a revolving mirror G. The reflected beam is then received either on a viewing screen H, or on a iilm within a iilm holder I. It will be understood that ii the mirror G is revolved and if the galvanometer reilector is not oscillating, the light diagram will be a straight line of light.` If the galvanometer reflector is oscillating the beam reilected will be at an angle to the beam which was reflected from the non-oscillating retlector.- When the reilector E is oscillatingA and the mirror G is rotating. the combined eiect of the two movements will be a curve-like diagram, and the amplitude oi' the 'departures from the straight line will be a measure of the amplitude of the oscillations of the galvanometer reilecton These oscillations are to be produced by variations in the characteristics of the subject of the investigation through the use of suitable mechanism influenced by such variations to produce variable electric currents, which currents are to be passed through the galvanometer coil carrying the mirror, the galvanometer coil being located in the iield ci the usual permanent magnet. For example, an engine indicator of a known kind and of the type illustrated for example in the patent to Peters, is subjected to the varying pressures within an engine cylinder in which a piston is reciprocating. These varying pressures produce variable electric currents in the circuit of the engine indicator, which varying currents when passed through the galvanometer coil cause the coil and its reilector to oscillate, the amplitude of the oscillations being a measure oi the pressure variations and being readable by the varying amplitudes of the visible light curve.

It will be understood that the above is illustrative of but one use of the instrument constituting the subject of this invention. The details of improvement have been designed, however, more particularly for use of the instrument with engine indicators and have been found to be particularly advantageous when so used.

'I'he disclosure of Fig. 1 is merely diagrammatic,

and since the several-parts therein designated by reference letters need not necessarily take the particular form l adopted in the instrument as more speciflcially illustrated in the other figures, these'reierence letters are not used on the other figures to designate the parts corresponding in a general way to the parts given reference letters in Fig; 1.

Coming now to thefdescription of the instrument in its speci-fic form and as illustrated in Figs. 2 to9inclusive, numeral designates the base of a rectangular box-like structure having end panels I3 and |5 and side panels |1 and |9. A top panel 2| completes the closure. One end of the base is formed with an upstanding wall 23. This wall 23 is of generally U-shaped outline when looked at from above as shown in Fig. 3. The bottom portion of the base of the U-shaped wall extends fromv the middle of the end of the base II part way to each side edge, whence the wall continues longitudinally fora short distance toward the other' end of thebase which has a slightly elevated platform or boss 25. The end panel |5 is secured' to the base and to its wall 23 by screws 21. Aligned openings 29 and 3| are seen in the end panel and wall, which openings are for the passage of a light beam from a source of light. The fastening means 21 also secure a lamp bracket 33 to the panel I5. The lamp bracket has a circular opening to receive a convex lens 35 secured in position in a suitable retainer 31. At 39 is a lamp bracket extension secured to the lamp bracket by fasteners 4 I. Within a recess of the extension is a lens shield 43 preferably of plate glass. The extension has an externalispherical surface 45 engaging a corresponding internal surfacel formed on a. divided double lamp bracket ball socket 41. A lamp bracket ball 49 is tightly fitted to the lamp houslng 5| carrying a conventional source of light, preferably an arc light. Suitable fastening means 53 are used to clamp the parts of the ball socket 41 upon the ball of -the lamp housing and upon the sphericalpart 45 of the bracket. By the adjustment of the lamp housing relative to the socket 41 the position of the arc may be changed at will, and by the adjustment of 41 together with the lamp housing relative to the extension 39 the beam from the source of light through the center of ball 49 may be brought into alignment with the principal focus of lens 35. -There is thus provided a conveniently adjustable means for positioning the light source relative to the instrument.

The light from the source after passing through the lens 35 then passes through openings 29 and 3| in the end .panel and the wall 23. After passing these openings the light then is transmitted through an adjustable shutter to be described below, the shutter being located between the side members of the U-shaped wall 23. A generally horizontally positioned light shield 55 is mounted on the top edge of the U-shaped wall adjacent the cnd panel I5. This shield is then curved downwardly between the side members of the wall and, adjacent its other end, it is secured to posts or projections 69. A slot 51 is cut in the shield as shown in Fig. 2 for the passage of the light beam from the shutter. The purpose of this shield is to prevent any reflected rays reaching the region of the revolving mirror which is located above the shutter. To the rear of the horizontal shield is a vertical light shield 58. This shield has a vertical slot 59 for the passage of the .light beam.Irgrn.tigersV tter, and it also has a horizontally elongated slot 62 above the slot 59. This wall shuts off from the region of the galvanometer all light except a beam which is transmitted through the shutter. The horizontal slot is for the passage of the beam of light from the oscillating reflector of the galvanometer. The top panel 2| is formed 1n parts, one part being in the form of a door 6| hinged as at 63 to the box. In its closed position this door engages a cross bar 85. In a depressed part of the door is a. lifting ring 81. The door may be maintained in open position by links 69 and 1| hinged to the door and the box, and also to each other and operably related to hold the door in open position in an obvious manner. 1 Slidable along the top panel 2| and over the door 8| is a film box base 13 having an opening 15 to register with a top panel opening 11 in one position of the film box base. Over the opening 15 is an arcuate viewing scrn 19. To the rear i of opening 15 is the film box 8 I. It will be understood that the base 13 has a second opening corresponding with opening 15 and located underneath the film box 8|. A slide 83 is used to cover the film within the film box in a well known man- 2 ner. When the part 13 is moved to the left from its position in Fig. 2 so that the box 8| is over the opening 11, the slide 83 may be removed and the lm within the box exposed to the reflected light beam just as in the case of the viewing screen as shown in Fig. 2. The correct position of the fllm box may be known by the position of the spring-pressed detent 85 as shown in Fig. 4. The f'llm within the box should be arranged to travel over an arcuate surface corresponding to 3 that of the Viewing screen 19, which film may be wound on suitable spindles 81 and 89 by the use of an operating handle not shown. Access to the lm is had by a removable cover 9|. No novelty is herein claimed for the film box per se 4 nor for the means for rolling the nlm on its spindles. For this reason no more complete showing is made of the details relating to the film box.

Each of the side members of the wall 23 is apertured to receive a bushing-supporting ring 93, 4 these rings being secured to the aforesaid side members of wall 23 by fastening means 95. 'Ihe rings 93 carry bushings 91 for the rotatable support of a mirror shaft 99. Retainer |0| is used to hold the shaft in position. Outside the panel 5 l1 a universal joint |03 of any preferred kind may be used to connect the mirror shaft 99 to a shaft |95 which projects in alignment with shaft 99 from a gear housing |01. If it be desired to mount this gear housing rigidly with the instru- 5 ment, a. bracket |89 may be used to support the gear housing which bracket may be attached to the instrument by suitable fastening means. Also extending into the gear housing is a shaft as shown in Fig. 3. This shaft is to be rotated 6 by a suitable connection with the driven shaft of the engine, the characteristics of which are to be investigated. Any desired gear ratio may be secured by the provision of a suitable gear train within the gear housing |01. It has been deemed 6 unnecessary to illustrate the gearing within the housing since no claim is being made for the specie gearing per se. Between the side members of the U-shaped wall 23 the shaft 99 is shaped to support a plurality of flat mirrors ||3. "I'he 7 number of mirrors may be as desired, the drawings showing six of said mirrors, this being a preferred form.

As to the galvanometer per se, no novelty is being claimed. As explained above when the 7 oscillograph is used with an engine indicator the iluctuating current from the indicator is conducted through the loop of wire located in the field of the galvanometer magnet. and this loop carries the osciliatingreilector. When the current passes through the loop of wire it is made to deflect by its reaction with the ent magnet. This causes a rotation of the tlector. The natural frequency of this galvanometer element is high enough so that very rapid current fluctuations cause corresponding voscillating movements of the reilector.

From the above description it will be understood that a beam of light from the source passing through the shutter is reflected by the galvanometer reflector to the revolving mirror which, as it revolves, causes a line of light to be described on the screen or film. This line will be a straight line as long as the galvanometer reflector does not oscillate. If, however. there are current fluctuations in the galvanometer coil, the coil osciilates as explained above and the direction of the reilected beam is changed. n the screen the longitudinal path of the beam produced by the rotating mirror and the transverse path produced by the oscillating reflector combine to produce a curve.' In this curve the amplitude of the departures from the longitudinal line serve to measure the amplitude of the oscillating movements of the reflector and therefore of the magnitude of the causes producing such oscillating movements.

It is desirable to know the condition of the galvanometer current and of the magnitude of the characteristics producing such current at predetermined positions of the moving parts of the subject under investigation. Speciilcally it may be desirable when making a light diagram of cylinder pressures to know the pressure at the upper and lower dead centers of the piston in its movement of reciprocation. To that end there is used a U-shaped member pivoted on its two sides toand within the rings 22,. This construction is illustrated in Fig. 3. The sides of the U-shaped member ||5 extend up from the shaft 22 toward the viewing screen, and a wire ||1 is connected to the extremities of the sides. A curved rack ||2 on one vside of the U-shaped member is in engagement with a pinion |2| on a pinion shaft |22 (see Fig. 2 and Fig. 7) rotatable in one side member of the U-snaped wall 22. Rotation of pinion shaft |22 operates to swing the U-shaped member ||5 about its pivot and with it the wire ||1. This rotation is effected 5;, by an adjusting shaft |25 shown in Fig. 3, which shaft is rotatably mounted in panel i2. The adjacent ends of shafts and |22 have removable interlocking parts to facilitate the assembly and removal of the panel I2. With the shutter in its open position. and with the piston in its position of upper dead center the shafts |25 and |22 may be rotated by means of a suitable handle |21 on shaft |25 until the wire ||1 intercepts the light beam, cutting olf the light from the viewing screen. When, thereafter, the engine is being tested and the curved light diagram is being examined, the wire ||1 will cut of! the lightbeam and make a break in the curve at the upper dead center position of the piston. To similarly shadow the light beam at the lower dead center position of the piston, a second U-shaped member |22 is used. This member |25 is shown in Fig. 2 and in Fig. 4. The drawings show it piv- .oted to member ||5 at |2| and there is provided an adjustable pin and slot connection at- |22 so that the wire |25 carried by the ends of the sides of member |25 may be variably located in predetermined positions. This position may be that corresponding to the lower dead center-position of the piston as explained above.

'I'he light beam reilected from the oscillating reilector of the galvanometer is ca used to pass through a cylindrical lens |21 on its path to the rotating mirror. This lens |21 is elongated as best shown in Fig. 7 to accommodate the variations in direction of the reflected beam resulting from the oscillationsl of the reflector of the galvanometer. The lens |21 is supported by a carrier |29 and posts |4|, the latter supported in the upper parts of the side members of the U-shaped wall 22. As will be seen from the drawings. these posts are positioned to locate the plane of the cylindrical lens at right angles to the plane defined by the several lines corresponding to the beams of light reflected from the oscillating reilector in its several positions of oscillation.

. For the purpose of determining 'the point `in the light diagram corresponding to the instant of ignition, resort is had to the expedient shown diagrammatically in Fig. 9. A small transformer is used to superimpose an induced current on the current through the galvanometer coil at the instant of ignition, and this superimposed current gives evidence of itself by producing a slight change in the angular position of the reflector, and consequently a slight change in the direction of the reflected beam. 'I'his is but momentary, but the curve on the light diagram is given a resulting irregularity or kick corresponding to the instant of ignition. To produce this effect the primary winding of a small transformer is included in the circuit through the battery, breaker. and ignition coil associated with the engine, and the secondary winding of the small transformer is in series with the engine indicator circuit which passes through the osclllograph element, that is through the galvanometer coil carrying the reflector. The number of turns in the windings is kept small enough to avoid interfering with the operation of the oscillograph. This is fully and clearly illustrated by Fig. 9. When the ignition breaker contact points open, a small induced current irregularity is registered on the light diagram.

The shutter is mounted on the base beneath the shield 55. The shutter itself is a brass cylindrical member |42. It has a diametrically located slit |45 for the passage of light. From the ends of the shutter extend axially pivots |41. The upper pivot seats rotatably in the recessed lower end of a screw |49. This screw is threaded into an upwardly directed and overhanging member |52 carried by a shutter bracket |52. The lower pivot |41 seats in a similar recess in the end of a base pivot member |5I. The base pivot member |5| is threaded into the shutter bracket |52, which rotates about a boss |55 formed onv the base as shown in Figs. 4 and 5. The base pivot member |5| extends beyond the bracket downwardly through the base within which it is rotatable. A spring |55 surrounds the extension of the base pivot member |5|, and engages the base and a head |51 secured to the extreme end of the base pivot member |5|'. -In this way the bracket |52 with the vparts carried thereby has a rotatable mounting relative to the base but is resiliently restrained from rotation by the action of the spring whereby frictional contact is maintained between the boss and the bracket. For rotating bracket |52 one portion thereof is provided with vertically spaced tongues IGI. Between the tongues is a trunion nut |63 in threaded engagement with a shutter adjusting screw |66, the latter rotated by a shutter adjusting shaft |61, there being an interlocking engagement between the shafts |66 and |61 as between the shafts |23 and |26 and for the same purpose.

An external hand grip |66 on shaft |61 is provided. A spring |1| is used as shown in Fig. 3 to hold the screw |66 in any position to which it may have been adjusted, and a spring |12 maintains the two shafts in interlocked relation. By the adjustment described the bracket i 63 is rotated and with it the shutter whereby more or less of the width of the shutter slot is rendered available for the passage of the light beam. Rotatable about a plane surfaced region of the upper screw member |66 is an arm or lever |13. In addition to the opening in |13, by which it is permitted to pivot freely on part |66, it has a second opening for the passage of the bent over end of a shutter opening rod |16, the latter removably connected to a manually operable shutter-ad- ,iustingV shaft, |11 extending to the outside of panel I6. 'I'he bent over end of rod |16 is so related to the shutter that when the rod |15 is pulled outwardly the shutter is rotated to locate the slot in its open position for the passage of the light beam as will be more fully explained below.

'I'he shutter bracket |63 carries also a support |16 for an electromagnet |6|. 'Ihe shutter |63 has secured thereto a soft iron keeper |63. 'I'he position of the electromagnet and the keeper relative to the shutter is such that when the electromagnet is energized and the keeper is drawn toward it, the slit of the shutter is in its open position, that is ln the path of the light beam from the source. As explained, the degree of opening is governed by the adjustment effected by shaft |66. To oppositely rotate the shutter to its inoperative or closed position where the slit ls positioned across the path of thc light beam, there is a spring |66 attached to a lug |61 on the bracket |63 and to the combined keeper and shutter. It will therefore be seen that the spring normally holds the shutter in closed position, and that the electromagnet when energized opens the shutter against the tension of the spring. The shutter may also be opened manually by the use of the rod |16 as stated above. The angular surface on the combined shutter and keeper resulting from the connection of the keeper to the shutter, forms an abutting surface which is engaged by the bent end of the rod, so that when the rod |16 is pulled this bent end engages the combined keeper and shutter and rotates the same to its open position, just as it is rotated to open position by the electromagnet. The shutter may therefore be held in open position as long as desired.

When photographing the light beam it may be desired to impress upon the film a single diagram, that is a diagram from a single one of the several surfaces of the rotating mirror, rather than to impress upon the lm a series of superimposed impressions. To that end the electromagnet is used to automatically open the shutter only long enough for a single impression and to thereafter permit the shutter to close under the lniluence oi' the spring |66. 'I'he automatic means is controlled by the rotation of the mirror itself as will be now explained.

To the end of shaft 66 is secured a shutter commutator or what may be called a cam |66. This cam is of insulating material and in the form of a threaded member |66. 'I'he cam has a contact wire located within its spiral surface and designated by numeral |6|. This wire may be made to contact with shaft 66, and it is to be engaged by a contact point on an arm |63, which arm contact point and wire are, while engaged, to close a circuit and energize the electromagnet. The circuit is not illustrated as it involves no patentable novelty. It requires merely a suitable electrical connection between the wire and the electromagnet, and also an electrical connection between the arm |63 and the electromagnet. one of such connections including a source of electric current. The arm |63 is connected to one end of a shutter switch contact shaft |66. A shutter switch base |61 is secured to panel I6 and is formed with lugs as shown in Fig. 2 for the guidance axially and rotatably of said shaft |66. Slidable through end panel I6 is a push rod |66 which is intended to engage and reciprocate shaft |66.v Inward reciprocation of shaft |66 under the inuencc of a push from rod |96 moves the arm |93 bodily from the commutator or cam |66. Pivoted to the shutter switch base |61 at |66 is a detent 26|. The detent has an inclined end face 263 and a notch 266. Shaft |66 has secured thereto a pawl 261 which is intended to engage in the notch 266. A` shutter switch tension spring 266 is connected to a post 262 on the detent 26|, and to a second post 266 on the hub of the lever arm |63. This spring is so positioned that it becomes tensioned by the rotation of shaft |66 as influenced by the action of the screw cam |66 upon the lower end of the arm |63 as the mirror shaft rotates. When the cam |66 has rotated suiilciently to carry the contact point of the arm |63 to that end (the left end in Fig. 4) of the cam screw remote from the end at which it started, which may be referred to as the first end, the rod |66 may be operated to push the shaft |66 and with it the arm |63 bodily so that the contact point of arm |63 leaves the threaded surface of the cam. At the same time the tension in spring 266 which was produced by the action of the cam in rotating shaft |66 operates to reversely rotate shaft |96 and to restore the end of arm |63 to a position over the above-mentioned rst end of the cam. 'I'he arm |63 is held in this oil"I position by the engagement of the pawl 261 in the notch 266. During a part of the movement of the arm contact point along the screw cam it is in engagement with the contact wire carried by the cam. During that period of engagement the circuit through the electromagnet is closed and the shutter is opened and the exposure is made. As soon as the two contact points on the lever and cam separate, the electromagnet is no longer energized and the spring |66 closes the shutter.

For the next exposure provision is made to trip the detent 26| and release the pawl which is holding the arm contact point oil' the cam. For that purpose a trip shaft 2|6 is guided in other lugs of the switch base |61 anda spring 2|| holds the trip shaft 2|6 in its outward position toward the panel i6. The trip shaft 2|6 has a coneshaped end 2|3 which is intended to engage the inclined face 263 of the detent. A push rod 2|6 is slidable through the end panel I6 and is manually operable to push the shaft 2| 6 against its spring 2|| to cause the cone 2|3 to engage and lift the detent 26| from the pawl 261, whereupon the spring 266 moves the contact arm |63 into contact with the cam |66 at the said ilrst end of irl the latter. As the shaft 99 rotates, the cam then rotates the arm and the contacting points may engage and produce another exposure through the energizing of the electromagnet as explained above. It will be understood that before this second exposure a new section of lm will be rotated into position unless it should be desired to superimpose one light diagram upon another. When it is desired to observe the phenomena either for the sole purpose of observation or preliminary to making a photograph, it is only necessary to lock the contact mechanism out of operation by pushing the rod |98 and permitting the detent and pawl to cooperate in holding the contact arm |93 out of engagement with the cam. With the observing screen 19 in position the rod |11 may then be pulled out to open the shutter and the light diagrams may be observed on the screen.

With an oscillograph as described and used with an engine indicator the said oscillograph panels may serve as the bases for the mounting of the engine indicator Wheatstone bridge and related accessory instruments such as a meter, resistance coils, and switches.

Among the more important advantages which result from the improved instrument are:

l. 'I'he mounting of the source oi light for convenient adiustment relative to the instrument.

2. The positive driving of the rotating mirror by the engine. The mirror shaft may be directly connected to the engine shaft or it may be connected by a gear box as shown in the drawings. The gear box may be mounted on a side panel as shown in the drawings or if it be desired to avoid communicating vibrations to the instrument, it may be separately mounted.

3. The operating mechanism including the electromagnetic shutter affords an automatic arrangement for making a single or a plurality of exposures.

4. The combined film holder and viewing screen afford a ready means to convert the instrument from a photographing device to one giving a visible picture.

5. The mechanical means for checlng the condition of the light curve at upper and lower dead centers constitute an especially useful feature in ,0 an instrument oi this kind.

point corresponding to the ignition is another valuable addition to instruments of this kind.

1. In an oscillograph, a rotating mirror, a surface upon which a light diagram is made by light reflected from said mirror, shadow-forming means to intercept the light beam between the mirror and the surface, and means to secure said light-intercepting means in predetermined positions corresponding to positions of parts of the mechanism being investigated.

2. In an oscillograph, a rotating mirror, a surface upon which a light diagram is made by light reflected from said mirror, means to intercept the light beam between the mirror and the surface, and means to secure said light-intercepting means in predetermined positions corresponding to positions of parts of the mechanism being investigated, said means having radial arms and a wire or the like connected to said arms to intercept the light beam.

3. In an oscillograph, a rotating mirror, a surface upon which a light diagram may be traced by light reflected ifrom said mirror during its rotation, a plurality of shadow-forming means to intercept the light beam, and means to secure each of said light-intercepting means in predetermined positions corresponding to positions of parts of the mechanism being investigated.

4. The invention dened by claim 3, each of said light-intercepting means carrying a shadow-making wire, one of said means being rotatably adjustable about an axis of rotation at the center of curvature of the said surface, and the other of said means being adjustable about a pivot carried i by the first of said means.

5. In a device for use with an engine indicator associated with an internalombustion engine having an ignition coil, said device including a galvanometer provided with an oscillating reilector, a rotating mirror and a surface to receive a light diagram, a transformer having a primary winding adapted to be connected in series with the primary winding of the ignition coil used and a secondary Winding constituting a part of the circuit from the engine indicator which circuit also includes the galvanometer coil whereby the points on the light diagram corresponding with engine ignition are indicated.

GERALD M. RASSWEILER. EDWARD J. MARTIN. 

